Display devices in which a cover glass is placed on a front surface of a display panel are known. As a result of providing the cover glass, the display panel can be protected, and design of the display device can be improved.
In recent years, operability of display devices have been improved by attaching a touch sensor (refer to JP 2013-122745 A, for example). With the touch sensor, various processing such as changing a display image and activating application software can easily be performed on a screen with a finger or the like touching the screen, and therefore a display device having high operability can be obtained. A touch-sensor-equipped display device is also referred to as a touch panel.
In the touch sensor, normally, the position at an X coordinate and a Y coordinate of an object that has touched the screen is detected, and the input would be determined based on these coordinates. Examples of a detection method of X and Y coordinates include an electrostatic capacitance type method in which an electrode is to be attached to a back surface of the cover glass, an optical type method in which a camera is to be attached to a side of the cover glass, and the like. In the optical type detection method, a frame is provided that protrudes forward farther than the cover glass in a periphery of the cover glass, and a small camera is embedded in a side portion of the frame. Therefore, since the frame protrudes farther than the cover glass, it is difficult to obtain a flat display device. On the other hand, in the electrostatic capacitance type detection method, the electrode needs only to be attached to the back surface of the cover glass and the frame does not need to protrude, and a display device having a flat surface can be easily obtained. In recent years, in touch-sensor-equipped display devices, a device that is thin and well designed is preferred, and in this case the electrostatic capacitance type method is advantageous.
In the electrostatic capacitance type touch sensor, a plurality of planar members are required to be disposed with high positional accuracy. For example, a touch sensor can be configured by laminating an electrode layer for detecting an X coordinate and an electrode layer for detecting a Y coordinate, and it is important that these electrode layers are overlaid, as much as possible, without any positional displacement. When the electrode layers are displaced, an accurate detection may not be performed. Also, the touch sensor is fixed by being bonded to the cover glass, and it is also important that the attachment position between the cover glass and the touch sensor does not include any positional displacement as much as possible. Also, because an input in the touch sensor is performed by an operator who has viewed the display in the display panel and follows the display, it is also important that the relative position between the touch sensor and the display panel does not include any positional displacement as much as possible.
A method in which a transparent adhesive tape that expresses adhesiveness on both sides thereof is used to bond members together in the touch-sensor-equipped display device is known. The members can be easily bonded together by using the adhesive tape. However, the method in which the adhesive tape is used requires that the members are overlaid while accurately aligning positions on a surface having adhesiveness, and because re-bonding normally cannot be performed, bonding together with high positional accuracy becomes difficult, specifically when the display area of the device increases.